Client proteins of the secretory pathway fold to their native structures in the endoplasmic reticulum (ER) through reactions that are catalyzed by chaperones, oxidoreductases, and other protein-modifying enzymes. However, under high secretory demand these ER-resident activities become overwhelmed, leading client proteins to accumulate in unfolded forms within the ER. This condition-termed ER stress-puts affected cells at increased risk for death. As such, unchecked ER stress is now recognized as being central to the development of various human diseases of cell loss, including neurodegeneration and Type 2 diabetes. Unfolded proteins in the ER trigger signaling pathways called the unfolded protein response (UPR). Under remediable levels of ER stress, the UPR sets in motion transcriptional and translational changes that promote adaptation. But when confronted with irremediable levels of ER stress, these adaptive measures fail and the UPR instead switches strategies to trigger programmed cell death-we refer to this outcome as the terminal UPR. Our overall goal for this R01 is twofold: (1) elucidate underlying molecular mechanisms through which the terminal UPR and oxidative stress synergize to cause pancreatic ?-cell degeneration, and (2) therapeutically target key nodes in the terminal UPR to protect against mouse models of diabetes. The elucidation of mechanisms connecting ER and oxidative stress signaling components holds the promise of developing novel drugs to treat diverse cell degenerative diseases, including diabetes.